Coulometry in resonator cavity of EPR spectrometer: Electrochemical oxidation of carbazole methyl derivatives

Abstract

Electrochemical reduction of carbazole, 3-methyl- and 3,9-dimethylcarbazole in acetonitrile leads to the formation of a layer of conductive, insoluble products on the electrode surface of a partially radical character. This phenomenon was studied by coulometry in the resonator cavity of an EPR spectrometer with simultaneous measuring of the spin concentration. With carbazole and 3-methylcarbazole, the radical particles are formed with a yield of about 2% with respect to the current passed, whereas with 3,9-dimethylcarbazole this yield is by an order or magnitude lower. The radical product adsorbed on the electrode is probably a sparingly soluble perchlorate of the cation radical of 3,3'- or 6,6'-bicarbazole. 3,6,9-Trimethylcarbazole gives on oxidation a relatively stable primary cation radical. Electrochemical oxidation of 9-methyl- and 3,6-dimethylcarbazole does not lead to radical products.